Dynamics of quantum systems embedded in a continuum

The relevance of the open quantum system formalism for the description of weakly bound nuclei far from the valley of stability, small droplets of neutral atoms, gas of trapped atoms, open microwave cavities and quantum dots is discussed. We describe nuclear structure and nuclear reaction studies in the shell model embedded in the continuum. This model is an extension of the multiconfigurational shell model including one-particle decay channels. The coupling to multi-particle decay channels, as e.g. in 'Borromean systems', is discussed in the alternative formulation of Gamow shell model in the complete Berggren basis. Simple schematical models are used in order to discuss the basic dynamical processes characteristic of open quantum systems. The generic features of these systems in different regimes of multiconfigurational mixing are illustrated by examples of weakly bound atomic nuclei, externally driven atoms and microwave cavities. (C) 2002 Elsevier Science B.V. All rights reserved.